Carburetor



3 Sheets-Sheet 1 R.' F. BRACKE ('JARBURETOR4 Filed April 15', 1937 Junel13., 1939.

June 13, 1939. RuF. BRACKE GARBURETOR Filed April 13, 1937 3Sheets-Sheet 2 'June 13, 1939.

R. F. BRACKE cARBUREToR Filed April 13, 1937 3 Sheets-Sheet 3 BJ MIM;

Patented June 13, 1939y 9 Claims.

My invention pertains to carburetors, and is more particularly concernedwith carburetors of the fuel lift type.

In non-fuel lift carburetors for automotive use, it is common to providea main fuel supply nozzle and an idling jet. This idling jet iscustomarily located on the engine side of the throttle valve, and takescare of the fuel requirements of the engine during idling operation. Aneedle l0 valve o r other adjustable means is commonly provided toadjust this idling jet. Both the main fuel supply nozzle and the idlingjet receive their fuel requirements from the float bowl of thecarburetor.

Various attempts have been made to provide a fuel lift carburetory withsuch an idling jet. In fuel lift carburetors, however, the float bowl ofthe carburetor is maintained under a degree of suction sucient to drawfuel thereinto from the main fuel supply tank, usually located at therear of the automobile. At full throttle operation the degree of suctionobtaining in the carburetor float bowl is greater than that obtaining atthe discharge end of the idling jet, with the result that g5 back feedof fuel and air occurs lfrom the idling jet to the float bowl of thecarburetor.

disadvantageous in that it destroys the delicate balance necessary toproper operation of a fuel lift carburetor.

Y An object of my invention is to provide a fuel lift vcarburetor withxan idling jet which overcomes the foregoing disadvantages.

Another object is to provide a fuel lift carburetor with an idling jetwhose supply of fuel is cut off by a throttle regulated valve underpredetermined conditions.

Another object is to provide a fuel lift carburetor of the dual type,and wherein each of two idling jets is provided'with an independentadjustment. A

Another object is to provide an idling jet having a control valvemechanism which functions to enrich the mixture supplied to the enginewhen the throttle valve is opened.

Another object is to provide a carburetor which is simple and economicalto manufacture, which will provide long and trouble-free service, andwherein the various control mechanisms may be independently adjusted.

Other objects and advantages will become apparent as the descriptionproceeds.

In the drawings:

Figure 1 is a longitudinal section of a carburetor embodying myinvention. 'I'his figure is taken on the line I-l of Figure 2.

This is:

(Cl. 26l--72) Figure 2 is an irregular horizontal section taken on theline 2--2 of Figure 1.

Figure 3 is a diagrammatic view wherein the relative positions oftheparts are distorted but wherein their functional relationship is easierto 5 follow.

Figure 4 is a fragmentary longitudinal section similar to Figure 1, butshowing a modified form of my invention. This figure is taken on theline 4-4 of Figure 5. 10

Figure 5 is a horizontal section taken on th line 5-5 of Figure 4.

I have shown my invention as being embodied in a fuel lift carburetor ofthe dual type. This carburetor has an air inlet I0 which may be 15provided with any suitable air cleaner or strainer, and which suppliesair to a pair of fuel feeding nozzlesl l2. Each of these nozzlesdischarges into a mixing chamber I4, and each mixing chambercommunicates with a throttle bore I6 leading to the inlet manifold ofthe automobile engine.

An airvalve I8 controls the supply of 'secondary air to the mixingchambers I4. In normal operation of the engine the quantity of fuelsupplied thereto is variably controlled by a pair of throttle valves 20,which are mounted on a common shaft 22 having attached to one endthereof a lever 24 provided with a ball head 26 adapted for connectionto the usual hand and foot controls 'of the automobile. This lever 24 isfurther provided with an adjustable screw 28 which engages a stop pin 30to determine the closed positions of the throttle valves 20.

Thetwo nozzles I2 are supplied with fuel from a common float bowl 32.This float bowl is pro- 35 vided with a threaded inlet 34 adapted tohave. secured thereto a pipe leading to the main fuel supply tank at'the rear of the. automobile. Such a pipe `is indicated at 36 in Figure 3of the drawings. The usual inlet valve 38 is provided to reg- 4() ulatethe supply of fuel to the float bowl from the main fuel supply tank,this inlet valve 38 being controlled in tum by the float 40 which ispivotally supported at 42. Y

All fuel passing from the oat bowl 32 to the 45 nozzles. l2 must passupwardly through a xed tube which is threadedly secured to the uppercasting 43 of the carburetor. This tube leads to a chamber 4l which isconnected with the individulil nozzlesl I2. respectively. by way ofpas:- sages l! and.

Each of .the nozzles I2 has a restricted throat terminating in a step54, and immediately below this step is a series of inclined passages 56lead- 55 ing to an annuluar space 58. This space `communicates with oneof the passages 58 or 52.

The secondary air valve I8 may be of any suitable type. In the drawings,however, I have shown an air valve consisting of a plate 68eccentrically mounted on a rod 62 pivotally supported in the casting 46.Attached to this rod 62are a pair of spaced weights 64, which tend tohold the plate 68 against the shoulder 66. The suction created beneaththe plate 68` tends to open this valve against the resistance of theweights 64.

The movements of the airvalve |8 are dampened by dashpot mechanismcomprising a cylinder 68 having' a piston 18 reciprocable therein. 'I'hepiston 18 has a piston rod 12 provided with a slot 14 which receives apin 16 extending between the two weights 64. 'Any movement of the airvalve I8 thus creates a corresponding movement ofthe piston 18. In thenormal operation of the carburetor the upper end of the cylinder 68 isclosed to atmosphere, whereas the lower end of this cylinder isconnected to the space beneath the secondary air valve I8 by means of asmall opening 18 of a size comparable to that made by a No. 60 drill.

The oat bowl 32 is normally maintained under sub-atmospheric pressuresby a booster 88. 'Ihis booster is in the form of a Venturi tube having arestricted throat provided withradial passages 82'communicating throughan annular chamber with a duct 84 leading to the top of the float bowl32. This booster 88 receives its air supply through a port 86 in ashiftable choke plate 88.

When the carburetor is operating under normal conditions, the plate 88is in Ithe position shown in Figure 1 of the drawings. The pot 68establishes communication between the inlet end of the booster 88 andthe chamber 88 formed by` n through an L-shaped inlet |88.

. 'I'he booster 80 discharges into the upper end of a cylindrical spaceI 82 which is divided into upper and lower parts by a metal cup |84having a-restricted orifice |86. A tapered pin |88 is located in theorice |86, and is attached to the lower end of`r the piston rod 12,whereby this 'pin shifts its vposition with the air valve I8. Thefunction of 4this pin |88 is to regulate the flow of air through theboos r 88, and thereby maintain the desired degree of suction in thefloat bowl 82 under all conditions of carburetor operation.

The lower end of the tubular space |82 is in communication with a duct||8 having `branches I I2 leading to both mixing chambers I4.

It will be understood that the chokel plate 88 is connected to the usualchoke control means located on the dash of the automobile, whereby thischoke plate may be shifted to facilitate starting of a cold engine. Suchshifting. of the choke plate 88 restricts or entirely cuts oi the-airsupply to the booster 88, thereby reducing the degree of suctionobtaining in the float bowl 32 and per.-

' passage I I6 leading to the upper end of the dashpot cylinder 68.Under lthese conditions the upper surface of the piston 18 is acted uponby atmosphere, whereas the lower surface of the piston is exposed to thesuction obtaining in the mixing chambers I4. This causes the piston 18toact as an additional means for closing the secondary air valve I8.

Below each throttle valve 28 I provide an idling jet ||8. Each idlingjet communicates with the lower end ofl a vertical conduit |28, and iscon.

trolled by an adjustable needle valve |22.y Each needle valve may beadjusted independently of the other, and is frictionally held inadjusted position by a spring |24. The upper end of each conduit |28communicates with 'the iioat bowl of the carburetor through means whichI shall later describe.

Back bleed would occur through an. opening |25 to the noatbow1 of thecarburetor if the associated idling jet |I8 were cut oi entirely by animproper adjustment of its needle valve |22.

In order to prevent such back bleed I provide each throttle bo're withan auxiliary idling jet |28. Each auxiliary idling jet |28 communicateswith a conduit |28, and is of ysmaller diameter than its associatedopening |26. 'I'he size of the auxiliary jets |28, however, issuiliciently large to prevent back bleed through the openings |26 l tothe float bowl of the carburetor in the event that the main idling jets||8, or either of them, is completely cut oif by an improper adjustmentof its needle valve |22.

The upper end of each conduit |28 is connected with the lower end ofkone of the inclined conduits |38 which lead to the opposite ends of across passage |32 (Fig. 2). .A metal plug having a metering orice |34 islocated adjacent each end of this cross passage |32, and' meters thequantity of fuel supplied to the idlingjets ||8 and |28. The centralportion of the cross passage |32 communicates with radial ports. |36formed in a stationary sleeve |38 press-fitted or otherwise secured inthe casting 46.

Inside the sleeve |38 there is a sliding tube |48 having radial openings|42 which connect the interior of the tube with the float bowl 32. 'I'hesliding tube |48 is also provided with a second series of radialpassages |44l connecting the interior of the tube with longitudinalslots |46 communicating with the radial ports |36 in the sleeve |38.When the parts are in the position shown in the drawings, the idlingjets I8 and |28 are capable of drawing fuel from the float bowl 32.

In order to prevent siphoning of the fuel from the oat bowl through theidling jets when the engine is not operating, I provide the upper endofthe sliding tube |48 with a small orifice |48 which functions as anair vent to break up any i siphoning action. When the idling jets areoperating to supply fuel to the engine, a small amount of air is drawnin through this opening |48 and mixes with the fuel supplied to theidling jets.

Additional air is supplied to the idling jets through the openings |26.

I shall now describe the means which I have provided for disconnectingthe idling jets from the float bowl of the carburetor whenthe-automobile reaches Ya speed of approximately twentyfive miles perhour upon a level road and with a. normal load. T'he upper end of thesliding tube |48 threadedly engages the lower end of a cap |58 which ispivotally secured to the lower end of a link |52. 'Ihe upper end of thislink is in turn pivoted to the end of an arm |54, non-rotatably securedto a shaft |56 by a pin |58.

'I'he shaft |56 is rotatably supported in bearings provided by the uppercasting 46, and one end of the shaft |56 extends outside of the c'asttheshaft |56. 'I'he levers |60 and |64 are adjustably connected by means ofa screw |66 which is held in adjusted position by a spring |68, whichalso eliminates any slack in the connection between the levers |60 and|64.

When the throttle valves 20 are opened to a position corresponding to acar speed of twentyve miles an hour on a level road with a normal load,the sliding tube |40 is raised to such a height that the ports |42 `inthe lower part of this tube are closed by the lower end of thestationary sleeve |38, and thus all communication between the idlingjets and the interior of the oat bowl 32 is cut off. The speed at whichthis cut-off occurs cariv be varied by adjusting the screw |66. Thesliding tube |40 is urged downwardly by a coil spring |10 which isinterposed between the upper casting 46 and a bar |12 carried by thelower end of the tube |40. l

This bar |12 also `,carries and reciprocates a metering pin |14. 'I'hismetering pin |14 has a relatively large cylindrical upper end |16 which,during idling operation of the engine, is located in a restrictedopening |18 formed in the tube 44, and thereby lreduces the amount offuel sup-A plied to the nozzles I2. This cylindrical portion of themetering pin 14 is made of appreciable length so that adjustment of thecut-off position for the idling jets does not vary the quantity ofmetering pin is located in the opening |18 and permits free flow of fuelto the nozzles I2.

The central position of the metering pin relativeto the orifice |18 isdetermined by a guide portion |84 which is located in the lower end ofthe tube 44. This guide portion has a passageway |86 which permits fuelto ow past the guide portion.

The bar |12 also supports and actuates the piston |88 of an acceleratorpump. This piston |88 is located in a cylinder |90 which extends downinto the float bowl 32 of the carburetor, and is secured to the uppercasting'46 by a threaded plug |82. The piston includes a leather cupwasher |94 whose lip is pressed against the cylinder wall by a coilspring |96.

The piston |88 has a hollow central portion |88 which communicates withthe interior of the float chamber through passages 200 and with theinterior of the cylinder |90 by wa'y of valve 202. 'I'he valve 202 islimited in its movement by a cross pin 204.

The piston |88 has a reduced stem 206 which is slidably received in anopening in the bar |12. The piston |86 is urged upwardly by a coilspring -208, the upward mvement of the piston under the influence ofthis .spring being limitedby a washer 2|0 secured to the lower end ofthe stem 206.

When the throttle valves are opened, the bar |12 is raised and thepiston |88 is moved upwardly. This upward movement forces fuel from the`cylinder upwardly..through the passage at the same rate as the bar 12.

2|2 and past the check-valve 2| 4 whichis normally held against its seatby a spring 2|6 resting against a support 2|8. 'I'he fuel forced pastthe Valve 2|4 flows through passageways 220 to accelerating nozzles 222.Each nozzle 222 com- 5 prises a tubular piece of metal having arestricted discharge opening. i y When the throttle valves are openedslowly, the spring 208 beneath the accelerator pump piston does notcompress, and this piston advances 10 However, when the throttle valvesare suddenly opened through an appreciable range of movement,theresistance offered by the fuel above the accelerator pump piston |88causes the spring 208 to compress so 15 that the accelerator pump pistondoes not move upwardly as fast as its actuating bar |12. After theactuating bar |12 stops its upward movement, the spring 208 expands andcontinues the upward movement of the piston |88. In this manner the 20injection of the accelerating charge is prolonged beyond the openingmovement of the throttle valves.

In my iriprovedcarburetor the idling jets also furnish additional fuelto the engine during an 25 opening movement of the throttle valveswhichtakes place within the operating range of the idling jets, that is,before these jets have been cut oif from communication with the floatchamber of the carburetor. During the normal opera- 30 tion of theidling jets, the fuel in the slots |46 of the sliding tube |40 does notrise vabove the ports |36 in the sleeve |38, and a mixture of fuel andair flows through these ports to the idling jets. When the throttlevalves are opened suddenly, the 35 sliding tube l|40 is suddenly raised,and the liquid fuel in the lower ends of the slots |46 is likewisesuddenly raised so that vit completely cuts off all air from the ports|36. Under the temporary condition thus created, only liquid fuelundiluted by 40 air passes through the ports |36 to the idling jets,thereby enriching the mixture supplied by these jets to the internalcombustion engine.

When the engine is idling, the secondary air valve I8 is closed, andmost of the air entering v4,5 the mixing chambers I4 ows through thenozzles |2. During the idling operation these nozzlesv draw little or nofuel from the oat chamber 32. Y 'I'he throttle valves 28 are practicallyclosed, and the mixing chambers are under a pressure only 50 slightlybelow atmospheric.

The idling jets ||8 and |28 are located on theu engine side of thethrottle valves, and are subjected to the high suction obtaining in theYengine manifold. These idling jets draw fuel from the 55 iloat chamberofthe carburetor. Thefuel which is withdrawn from the float chamber ismixed with a slight amount of air drawn into the vent |48 at the upperend of the sliding tube |40.

Additional air is supplied through openings |26 60 for mixture with thisfuel before it is discharged through the idling jets ||8 and |28. Evenduring idling operation, the throttle valves 20 are not entirely closed,and a slight amount of air flows therepastfor. mixture with the fuelsupplied through the idling jets. The richness of the ing chambers I4,thereby supplying additional air thereto. The throat of the booster 88is connected by means of radial ports 82 and passage 84 with the upperend of the float chamber 32 to withdraw air and vapor therefrom.

'I'he degree of suction maintained in the float chamber by the booster88 is regulated in part by the tapered pin |88 which varies the flowthrough the booster 80 and thereby varies the suction created bythisbooster. Under all ordinary conditions of engine operation thedegree 'pf suction in the float bowl is suilcient to draw fuel thereintofrom thel main fuel supply'tank, normally located at the rear of theautomobile. During starting of a cold engine the booster 88 may berendered entirely ineffective by shifting the choke plate 88 so that theinlet tothe booster is cut off. Such shifting of the choke plate alsoadmits atmospheric air to the upper end of the dash-pot cylinder 88, andthis air acts Iupon the piston v1I) more firmly to urge the secondaryair valve I8 toward closed position. Such positioning of the chokeplate, however, is used only during starting and while the engine isstill cbld.

As the throttle valvesI 20 are opened to cause the engine to operate atspeeds faster than idling speed, the nozzles I2 become effective tofurnish greater and ever greater proportions of the fuel requirements ofthe engine. When the engine is operating at a speed of approximatelytwentyfive miles per hour on a level road and under normal 'roadconditions, the nozzles I2 assume the entire burden of furnishing all ofthe fuel requirements of the engine. At this point the sliding tube |48has moved upwardly to such a position that the ports |42 are closed bythe lower end of the sleeve |38. thereby cutting off communicationsbetween the idling jets and the carburetor float bowl and renderingthese idling jets inoperative. This same opening movement of thethrottle valves raises the metering pin |14 in its associated-orifice|18 so that it offers less restriction to the ow of fuelto the nozzlesI2.

. If the throttle valves are opened suddenly for the purpose ofaffording rapid engine acceleration, the piston |88 of the acceleratorpump forces fuel into the mixing chamber through the ac-A celeratingnozzles 2,22. Where the accelerating movement of the throttle valves issudden, the spring 288 Vwhich actuates the accelerator pump pistoncompresses, and the pumping action of the accelerator pump piston isprolonged beyond the opening movement of the throttle valves. This qprevents choking of the engine by the too sudden supply of a largequantity of fuel through the accelerating nozzles. Upon a subsequentclosing of the throttle valves, the accelerator pump piston descends inits cylinder, and during this movement the valve 282 opens to admit fuelto the cylinder |88 above the accelerating pump piston. Where a suddenopening movement of the throttle valves occurs within the range ofoperation ofthe idling jets, the sudden upward movement of the slidingtube |48 carries undiluted liquid fuel above the ports |36 leading tothe idling jets. This temporarily provides the idling jets withadditional quantities of fuel which facilitate the accelerating actionof the engine.

When the throttle valves 28 are opened, the degree of suction obtainingin the mixing chamhers is increased sumciently to open the secondaryalrvalve against the closing action of the weights 84. As the throttlevalves 28 are opened wider, the secondary air .valve I8 also increasesits opening to admit additional air therepast, When the throttle valvesare fully opened, the secondary air valve I8 is also opened to itsfullest extent.

When the throttle valves 28 are fullyopened, the degree of suctionobtaining in the mixing chambers I4 is the same as that obtaining at theoutlets to the idling jets "which are located below these throttlevalves.` During Such full throttle operation the idling jets andopenings |28v are exposed to a degree of suction which is less than thatexisting in the iloatbowl 32,/but no back bleed to the float bowl canoccur because the communication between the float bowl and the openings|26 and idling jetsV II8 and |28 have been cut off by the movement ofthe sliding tube I 40. The point at which this cut-off occurs can beregulated by adjusting the screw-|88. Such regulation of the cut-offdoes not vary the operation of the accelerator pump, nor does it changef the resistance of the'economizer pin |14 to fuel ceives its supply offuel and air from a vertical conduit |28'. This conduit has an air inlet|26 communicating with a mixing, chamber of the carburetor. The upperend of each conduit |28 is connected by a transverse port |29 with ahorizontal passage |38 which connects with one end of the cross passage|32.

The central portion of passage |32 communicates with the interior of thetube |38 by way of ports |36'. The tube |88' has a larger bore |39which. communicates with the float bowl of the carburetor by way of asmaller bore I4 I A solid rod |40' extends through the tube |88' and hasits upper end attached to the cap |58. The lower end of this rod carriesa bar |12. The rod |48' has a groove |43' which maintains communicationbetween the float bowl of the'carburetor and the larger bore |38' whenthe automobile engine is idling or driving the automobile at speedsbelow 15 miles per hour and under normal load.

In this embodiment of .my invention the needle valve |22 for controllingeach idling jet is so located that it controls the admission of liquidfuel to the transverse port |29. Each needle valve is maintained inadjusted position by its associated spring |24. I have found that wherethe needle valves/for controlling the idling jets are so arranged thatthey'regulate the flow of' liquid fuel only instead of a mixture of fueland air, more stable engine operation is obtained at idling speeds.

In order to prevent siphoning of' the fuel through the idling Jets whenthe engine is ai rest, I provide the upperend of each conduit |28' witha very small duct l'which connects with a secondary air inlet Just belowa. secondary air valve. In practice 1 have obtained excellent resultswhere the ducts |48' are made with a No. 75 drill, the Aopenings |28with a No. 'I0 drill. and the idling lets H8' with a No. 65 drill.

Subject matter disclosed but not claimed herein is claimed in mycopending application Serial No.

' 273,853, led May 16, 1939.

fuel, a mixing chamber into which said nozzle discharges, a throttlevalve 'associated with said mixing chamber, an idling jet below saidthrottle valve, conduit means including a valve for connecting saididling jet with said float chamber, an operating connection between saidlast mentioned valve and said throttle valve, an accelerating nozzledischarging into said mixing chamber, an accelerating pump connectedwith said accelerating nozzle, economizer means interposed between saidfirst mentioned nozzle and said float chamber, means connecting saidconduit valve with said economizer means and accelerator pump, and abooster for maintaining said float chamber under subatmosphericpressure.

2. In a fuel lift carburetorof the class described, the combination of anozzle, a float chamber from which said nozzle is supplied with fuel,means including a metered orifice connecting said nozzle with said floatchamber, an economizer pin located in said orifice, said economizer pinhaving a cylindrical part restricting flow of fuel to said nozzle duringidling operation of an engine to winch said carburetor is attached, anidling jet, conduit means connecting said idling jet with said floatchamber, a valve in said conduit means automatically operative to cutoil said idling jet from said float chamber when a predeterminedcondition of carburetor operation is reached, means connecting saideconomizer pin with said valve for movement therewith, means foradjusting said valve without disturbing the restrictive function of saideconomizer pin during idling operation ofthe engine, means for operatingsaid valve and economizer pin, and a `booster for maintaining said floatchamber under sub-atmosv pheric pressure.

3. Ina fuel lift carburetor of the class described, the combination of afloat bowl adapted to hold a quantity of fuel, means for maintainingsaid float bowl under sub-atmospheric pressure,

a main nozzle supplied with fuel from said float bowl, a conduitconnecting said nozzle with said, float bowl, said nozzle being capableof drawing fuel from saidA float bowl under all conditions of carburetoroperation, an idling jet supplied with fueljfrom said float bowl, asecond conduit connecting said idling jet with said float bowl, theabsolute pressure in said idling jet Vbeing greater under, certainconditions of carburetor operation than the absolute pressure in saidoat bowl whereby under said conditions of carburetor operation backbleed into said float bowl through said second conduit would normallyoccur. valve means controlling communication between said ioat bowl andidling jet, and automatic means operable upon creation of apre-determined con' dition of carburetor operation to closel said valveand prevent back bleed Ainto said float bowl.

4. In a fuel lift carburetor of thel class de scribed, the combinationof a float bowl adapted to hold a quantity of fuel, means formaintaining fuel from said float bowl under all conditions of carburetoroperation, an idling jet Supplied with fuel from-said float bowl, asecond conduit connecting. said idling jet with said float bowl, theabsolute pressure in said idling jet being greater under certainconditions of carburetor operation than thel absolute pressure in .saidfloat bowl whereby under said conditions of carburetor operation backbleed into said float bowl through said second conduit would normallyoccur, valve means controlling communication between said quantity offuel, means for maintaining said float bowl under sub-atmosphericpressure, 4a. main nozzle supplied with fuel from said float bowl, aconduit connecting said nozzle with said float bowl, said nozzle beingcapable of drawing fuel from said float bowl under all conditions ofcarburetor operation, an idling jet supplied with fuel: from said floatbowl, a second conduit connecting said idling jet with said float bowl,said second conduit having an air inlet, the absolute pressure in saididling jet being greater under certain conditions of carburetoroperation than the absolute pressure in said oat bowl whereby under saidconditions of carburetor operation back bleed into said float' bowlthrough said second conduit would normally occur, valve means in saidsecond conduit to prevent back bleed therethrough, said valve meansbeing located between said oat bowl and said air inlet, a throttle valvecontrolling communication between said main nozzle and an internalcombustion engine -to which said carburetor-is attached, and aconnection between said throttle valve and said firstmentioned valve toclose the latter when said throttle valve is opened a predeterminedamount.

6. In a fuel lift carburetor of the class described, the combination ofa oat bowl adapted to hold a quantity of fuel, ,means for maintainingsaid float bowl under sub-atmospheric pressure, a main nozzle suppliedwith fuel from said float bowl, a conduit connecting said nozzle withsaid float bowl, said nozzle being capable of drawing fuel from said oatbowl under all conditions of carburetor operation, an idling jetsupplied with fuel from said iloat bowl, a second conduit connectingsaid idling jet with said float bowl, the absolute pressure in saididling jet being greater under certain conditions of carburetoroperation than the absolute pressure in said float bowl whereby undersaid conditions of carburetor operation back bleed into said float bowlthrough said second conduit would normally occur, valve means forclosing said second conduit to prevent back bleed therethrough, saidsecond conduit having a portion located above said valve, a throttlevalve controlling communication between `said main nozzle and aninternal combustion engine to which said carburetor is attached, and aconnection between said throttle valve and said mst-mentioned .valve toclose the latter when said throttle valve is opened a predeterminedamount.

7. In a fuel lift carburetor of the class described; the combination ofa float bowl adapted the combination of a float bowl adapted to hold ato hold a quantity of fuel, means for maintaining said float bowl undersub-atmospheric pressure, a main nozzle supplied with fuel from saidfloat bowl, a conduit connecting said nozzle with said iloat bowl, saidnozzle being capable of drawing fuel from said float bowl under `allconditions through, a throttle valve controlling communication betweensaid main nozzle and an internal combustion engine to which saidcarburetor is attached, and a connection between said throttle valve andsaid first-mentioned valve to close the latter when said throttle valveis opened a predetermined amount.

.8. In a fuel lift carburetor of the class described, the combination ofa oat bowl adapted to hold a quantity of fuel, means for maintainingsaid float bowl under sub-atmospheric pressure, a main nozzle suppliedwith fuel from said iioat bowl, a conduit connecting `said nozzle withsaid float bowl, said nozzle being capable of drawing fuel from saidfloat bowl under all conditions of carburetor operation, an idling jet'supplied with fuel from said float bowl, a second conduit con necting'.said .idling jet with said float bowl, said second conduit having aportion located above the fuel in said float bowl, the absolute pressurein ,said idling jet being greater under certain conditions of carburetoroperation than the absolute pressure in said float bowl whereby undersaid conditions of carburetoroperation backbleed into said float bowlthrough said second conduit would normally occur, valve means in saidfloat bowl for closing said second conduit to prevent back bleedtherethrough, said valve means being submerged in the fuel in said floatbowl, a throttle valve controlling communication between said mainnozzle 4and an internal Acombustion engine to which said carburetor isattached, and a connection between said throttle valve and saidfirst-mentioned valve to' close the latter when said throttle valve isopened a predeterminedamount.'

9. In a fuel lift carburetor of the class de-4 scribed, the combinationof a float bowl adapted to hold a quantity of fuel, means formaintaining said float bowl under sub-atmospheric pressure, a mainnozzle supplied with fuel from said float bowl, a conduit connectingsaid nozzle with said float bowl, said nozzle being capab1e of drawingfuel from said float bowl under all conditionsvof carburetor operation,an idling -jet supplied with fueifrom said float bowl, a second conduitconnecting said idling jet with said float bowl, the absolute pressurein said idling jet being greater under certain conditions of carburetoroperation than the absolute pressure in said float bowl whereby undersaid conditions of carburetor op- ROBERT BRACKE.

- eration back bleed into said float bowl through

